The present invention broadly relates to switch actuating mechanisms and, more specifically, pertains to a new and improved construction of an actuating mechanism for an electrical switch with pressure contacts, especially for a vacuum switch.
Generally speaking, the actuating mechanism of the present invention is for an electrical switch having pressure contacts and especially for a vacuum switch having pressure contacts and comprises: means for longitudinally translatably guiding a contact plunger of the electrical switch in the direction of a switching stroke; a reciprocatingly drivable actuating rod having at least one end; a connecting rod having a first end and a second end; slide means for pivotably interconnecting the end of the actuating rod and the first end of the connecting rod; pivot means for pivotably interconnecting the contact plunger and the second end of the connecting rod; a stationary guideway engaging the slide means for constraining a joint path of motion of the end of the actuating rod and the first end of the connecting rod; and a compression spring acting upon the contact plunger and arranged to be compressed by an engagement position of the switching stroke of the contact plunger.
An actuating mechanism of this type is known, for instance from the German Petty Patent No. 8,109,229, published Aug. 6, 1981. In this known actuating mechanism the linkage comprises a bell crank. An S-shaped guideway is formed in the end region of one arm of this bell crank. A stationarily anchored pin engages in this S-shaped guideway and an actuating rod is pivotably connected to the end of the other arm. The pivot axis of the bell crank is fastened to a plunger which is longitudinally translatable coaxially with the contact plunger, which is also longitudinally translatable. When the bell crank is pivoted, its pivot axis is raised or lowered since the stationary pin engages in the S-shaped guideway. When the stationary pin is in the middle region of the S-shaped guideway, i.e. the actuating mechanism is situated between the engagement position and the disengagement position or vice versa, the counterforce generated by the compression spring surrounding the plunger generates, in cooperation with the S-shaped guideway, shearing forces on the pivot axis of the bell crank fastened to the plunger. The shearing forces must not only be taken up by this pivot axis but also by the guide ends of the plunger and furthermore load the plunger in bending.
In relation to the shearing forces acting on the plunger, analogous remarks apply to the actuating mechanism for a vacuum switch which is to be found in the U.S. Pat. No. 4,225,765, granted Sept. 30, 1980. This actuating mechanism does not comprise an S-shaped guideway.